Operations in which wood and other materials such as plastics are cut by a power tool require the workpiece to be precisely positioned relative to the cutting blade or bit of the power tool in order to achieve the desired results. This is especially true when the workpiece to be cut is to be mated with other pieces such as grooves made for dovetail and finger (or box) joints, generally made by a router type tool, or dado cuts for interlocking edges, generally made by a table saw.
It is occasionally necessary to stop a groove cut or through cut within a workpiece. When several of these cuts are to be made in parallel it is desirable to have a movable guide (such as a fence), which is tied to one reference axis but is movable along a second axis perpendicular to the first axis, and is marked with some type of reference mark to ensure uniformity of the length of the groove or cut.
A fence helps in making parallel cuts by helping to guide the workpiece through the cutting tool blade while one edge of the workpiece is maintained in abutting relationship with the fence. When a previously made reference mark on the fence is reached, the operator retraces his path or carefully removes the workpiece from the cutting tool and resets the fence for a new cut. When a reference mark is correctly used to locate the stopping point for several parallel cuts, the ends of the cuts stop at points which collectively form a line. If the cuts are not made uniformly, deviations from the normally straight line will be observed. In the prior art this happens often.
According to prior practice, a stop block has been used to help in stopping workpieces at a reference mark. A stop block is clamped, with a C-clamp, to a location on the fence or table surface to act as a physical stop corresponding to a reference mark. When the workpiece reaches the clamped stop block, the location of which has been set by the operator, the cut is complete. The operator then removes the workpiece and if necessary, readjusts the location of the stop block and/or fence for the next cut. When it is necessary to make several identical or nearly identical pieces with cuts of several different lengths, the operator may have to clamp and unclamp the stop block several times to provide the correct block location for those various cuts.
In the prior art, an inverted T-shaped slot has been provided in a fence to assist in attaching a stop block. A nut and bolt clamping arrangement has been used to hold and clamp the stop block in place at various locations along the fence as needed. Generally a large clearance is provided between the T-slot and any T-bolt or T-nut that is engaged in the slot for tightening. Because of this large clearance, every time the stop-block is moved there is a possibility of misaligning the stop block with the slot and face of the fence when the stop block is reclamped, when compared to its alignment at previously clamped locations. A great disadvantage is that it is time consuming and cumbersome to reposition the stop block with the degree of accuracy and repeatability that is required to fabricate complex joint structures.
When a stop block is clamped to the fence, it also rests on or leaves a very small gap between it and the working surface (table). As a result, chips which are generated by the cutting of the workpiece collect around the stop block. These chips tend to randomly lodge (or jam) in the corner between the fence and the workpiece facing the cutting tool. While a workpiece is being cut these chips randomly collect in this corner and tend to act as shims between the fence, the stop block, and the workpiece causing undesirable random discrepancy between workpieces, i.e. those cut "shimmed" verses those cut "un-shimmed".
Temporary marks or indicia made by an operator on a fence have been used to provide some degree of repeatability of cuts made by a cutting tool in cooperation with a fence. However, the disadvantage with this prior art is that there has been no permanent reference mark (or indicium) corresponding to the location of the cutting tool or means for easily locating a stop block adjacent to said strip. A lack of reference to the location of the cutting tool has often caused operators to run past their mark causing the workpiece or push fixture to be damaged by over cutting. This can also create an unsafe situation. When an operator is manually pushing the last portion of a workpiece through the cutting tool and he does not know precisely where the cutting tool is located, the possibly of injury to the operator is increased.
A pusher piece is often used to provide the operator with some degree of safety while pushing the workpiece through the cutting tool. However, when the location of the cutting tool is not precisely known and the pusher piece generally rests on the working surface (through which the cutting tool protrudes to make its cut), the pusher piece is often damaged as a result of the cutting tool cutting through the workpiece and into the pusher piece as it pushes the workpiece along. Cutting into the pusher piece is undesirable as it damages the pusher piece which may render it useless for future cuts.
It is occasionally necessary to hold workpieces vertically for an end cutting operation to produce dovetail or finger corner joints. A modified pusher piece has been used in the prior art to act as a fixture to hold the workpiece clamped vertically while it is moved past the cutting tool to form corner joints If these pieces are not held firmly and uniformly as they are guided along the fence or if they are not guided along the fence uniformly, faulty non-uniform non-repeatable cuts often result.